1. Field of the Invention:
The present invention relates to an apparatus for producing chips from logs of timber.
2. Description of the Prior Art:
Chippers of drum type are generally known in the art. Such chippers are disclosed in Japanese Patent Publication Nos. 21120/1967, 26321/1968 and 7081/1974, for example. Each of the chippers of this type includes a drum having a hollow portion formed therein which receives chips cut out. These chips tend to cling to the inner periphery of the drum under the influence of centrifugal force when the drum is rotated so that they will be difficult to remove out of the drum. In view of such circumstances, the drums in the chippers must be rotated at extremely low speed, for example at 25 to 120 rpm. This means that the productivity thereof is restrained. Furthermore, the chippers of drum type have to use logs of timber having a constant length.
A chipper having frusto-conical cutting tools is also well known in the art. Each of the frusto-conical tools includes a frusto-conical body having a plurality of cutting blades disposed on the outer peripheral surface thereof along a spiral path. Two of such cutting tools are located on the opposite sides of a log of timber to be chipped. Chippers of this type are disclosed in Japanese Patent Publication Nos. 15563/1968 and 24479/1973, for example. Each of these disclosed chippers is intended to produce square lumbers as well as chips from logs of timber. They are not designed to chip a whole log of timber.
Japanese Patent Publication No. 15562/1968 discloses a chipper consisting of a frusto-conical drum which is provided with a plurality of cutting blades disposed on the peripheral surface thereof along a spiral path. In such a chipper, a log of timber is fed axially at a fixed angle relative to the frusto-conical drum to produce chips cut out parallel to the fibre direction of the timber. In order to avoid that the interior of the drum receives the chips, the chipper is provided with a pocket adjacent to each of the cutting blades. Therefore, this chipper cannot obtain chips having uniform shape and size because of the hollow space created therein. Moreover, the frusto-conical drum is difficult to manufacture and also very costly.
Chips, particularly for cellulose pulp woods or fiberboards, are required to be of uniform size and subjected to no damage in any wood fibre thereof. None of the inventions disclosed in the abovementioned Japanese patent publications satisfies these requirements.